Two-Stage Ditch Idea Gains Momentum in Indiana

Better design to prevent erosion during big rain events, conservationists say.

Published on: Dec 26, 2011

Don't let the fact that The Nature Conservancy is promoting two-stage ditches cause you to reject them out of hand. The Nature Conservancy may be an environmental group, but they typically work hand-in-hand with farmers and often soil and water conservation groups to improve the environment.

In the past in northern Indiana, they have promoted programs that included cost-share and monetary guarantees for those that tried no-till. The program was successful.

Currently, the group is endorsing two-stage ditches. They believe it's a win-win for farmers and the environment. After reviewing the concept, it's hard to argue.

The typical farm drainage ditch has a V-shaped architecture. While they work fine under normal circumstances, and can handle water from tile outlets, during big rain events there is no place for excess water to go. Once it overflows the banks, it back up in fields, causing erosion and sediment loss when the flooding subsides. Those sediments carry nutrient particles with them into the water system. Sediment is still the number one pollutant in Indiana rivers, streams and ditches.

Nature Conservancy officials say a two-stage design mimics a more natural stream channel, even though it's an artificial ditch installed for drainage. The current stream channel on a ditch remains intact. To turn it in to a two-stage system, floodplain benches are added on either side. That creates storage for water during heavy rain events when the ditch simply can't handle the flow rushing in from the watershed around it. The water stays within the confines of the ditch and its overflow benches.

Estimates are that a two-stage ditch covering a one-half mile stretch in a typical installation in Indiana could save 53 tons of sediment from reaching waterways each year. That's possible because the banks of the main ditch remain stable and don't erode as with a normal, farm drainage, v-bottomed ditch. Bank failure is much less common with this system.